CN116666764B - Electrolyte for sodium ion battery and sodium ion battery - Google Patents

Electrolyte for sodium ion battery and sodium ion battery Download PDF

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CN116666764B
CN116666764B CN202310928452.5A CN202310928452A CN116666764B CN 116666764 B CN116666764 B CN 116666764B CN 202310928452 A CN202310928452 A CN 202310928452A CN 116666764 B CN116666764 B CN 116666764B
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electrolyte
additive
sodium
ion battery
carbonate
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CN116666764A (en
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陈雷
李哲
汤葱葱
刁继波
范敏
王雪扬
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Jiangsu Zhongna Energy Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)

Abstract

The application discloses electrolyte for a sodium ion battery and the sodium ion battery. The electrolyte comprises a nonaqueous organic solvent, sodium salt and an additive. The nonaqueous organic solvent comprises a cyclic carbonate compound and a chain carbonate compound; the additive includes a first additive including sodium fluoride, sodium carbonate, and sodium oxide. The electrolyte provided by the application can improve the cycle performance of the sodium ion battery and reduce the gas yield of the sodium ion battery.

Description

Electrolyte for sodium ion battery and sodium ion battery
Technical Field
The application relates to the technical field of batteries, in particular to electrolyte for a sodium ion battery and the sodium ion battery.
Background
Compared with lithium, sodium in nature has richer reserve and lower price, so the sodium ion battery has wide application prospect and is expected to form complementary and effective substitution with the lithium ion battery. However, the current-stage sodium ion battery has poor cycle performance, particularly at high temperature, and also easily produces gas at high temperature.
Disclosure of Invention
The application provides an electrolyte for a sodium ion battery and the sodium ion battery, which can improve the cycle performance of the sodium ion battery and reduce the gas production of the sodium ion battery.
In a first aspect, the present application provides an electrolyte for a sodium ion battery, comprising a nonaqueous organic solvent, a sodium salt, and an additive, the nonaqueous organic solvent comprising a cyclic carbonate compound and a chain carbonate compound; the additive includes a first additive including sodium fluoride, sodium carbonate, and sodium oxide.
By adding sodium fluoride, sodium carbonate and sodium oxide into the electrolyte at the same time, the compactness and uniformity of the SEI film can be improved, and the dissolution degree of the SEI film is reduced, so that the consumption of the electrolyte and sodium ions can be reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be improved, and the gas yield of the sodium ion battery can be reduced.
In some embodiments, the first additive is present in an amount of 0.042 to 84ppm by mass based on the total mass of the electrolyte.
In some embodiments, the sodium fluoride is present in an amount of 0.01 to 25ppm by mass based on the total mass of the electrolyte.
In some embodiments, the sodium carbonate is present in an amount of 0.01 to 40ppm by mass based on the total mass of the electrolyte.
In some embodiments, the sodium oxide is present in an amount of 0.01 to 25ppm by mass based on the total mass of the electrolyte.
When the mass content of the first additive is within the above range, the compactness and uniformity of the SEI film can be further increased, and the dissolution degree of the SEI film can be reduced, so that the consumption of electrolyte and sodium ions can be further reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas production amount of the sodium ion battery can be further reduced.
In some embodiments, the mass ratio of the sodium fluoride, the sodium carbonate, and the sodium oxide is (0.6-7.1): 1-17.1): 1 based on the total mass of the electrolyte.
By adjusting the mass ratio of sodium fluoride, sodium carbonate and sodium oxide in the above range, the compactness and uniformity of the SEI film can be further increased, and the dissolution degree of the SEI film can be reduced, so that the consumption of electrolyte and sodium ions can be further reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas yield of the sodium ion battery can be further reduced.
In some embodiments, the mass ratio of the sodium fluoride to the sodium carbonate is (0.3-2.0): 1.
When the mass ratio of sodium fluoride to sodium carbonate in the electrolyte is within the above range, dissolution of NaF in the SEI film can be reduced, so that stability of the SEI film can be further improved, cycle performance of the sodium ion battery, particularly cycle performance at high temperature, can be further improved, and gas production amount of the sodium ion battery can be further reduced.
In some embodiments, the additive further comprises a second additive comprising one or more of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), 1, 3-propenesulfonic acid lactone (PST).
By combining the first additive and the second additive, the compactness and uniformity of the SEI film can be further increased, and the dissolution degree of the SEI film can be reduced, so that the consumption of electrolyte and sodium ions can be further reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas production amount of the sodium ion battery can be further reduced.
In some embodiments, the second additive is present in the electrolyte in an amount of 0.5% to 5% by mass.
When the mass content of the second additive in the electrolyte is in the above range, the electrolyte can have better high-temperature stability, and a denser and uniform SEI film can be formed on the negative electrode, so that the high-temperature performance of the sodium ion battery can be better improved.
In some embodiments, the second additive comprises Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and 1, 3-propenolactone, and the mass ratio of the vinylene carbonate, the fluoroethylene carbonate, the ethylene sulfate, and the 1, 3-propenolactone is (0.5-3): 0.2-1.
When the second additive in the electrolyte comprises the above components, the stability of the sodium ion battery at high temperature can be further improved.
When the second additive is in the above range, VC may preferentially form NaF and Na on the surface of the anode 2 CO 3 Therefore, the SEI film can be synergistic with the first additive, and the film forming speed and uniformity of the SEI film can be improved.
In some embodiments, the mass ratio of the first additive to the second additive is (1.2X10) -6 - 1×10 -2 ）:1。
In some embodiments, the mass ratio of the first additive to the second additive is (6.2X10 -6 - 6.2×10 -4 ）:1。
When the ratio of the first additive to the second additive in the electrolyte is within the above range, a compact and uniform SEI film can be rapidly generated on the surface of the negative electrode through the synergistic combination of the first additive and the second additive, so that the dissolution and breakage of the SEI film in the use process of the sodium ion battery can be reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas yield of the sodium ion battery can be further reduced.
In some embodiments, the mass ratio of the cyclic carbonate compound to the chain carbonate compound is (0.2-0.7): 1.
By adjusting the mass ratio of the cyclic carbonate compound to the chain carbonate compound within the above range, the electrolyte can have high ionic conductivity, thereby being beneficial to improving the cycle performance and/or the rate performance of the sodium ion battery.
In some embodiments, the sodium salt comprises NaPF 6 Sodium difluorooxalato borate (NaODFB), naClO 4 、NaBF 4 、NaAsF 6 、NaSO 3 CF 3 、Na[(FSO 2 ) 2 N]、Na[(CF 3 SO 2 ) 2 N]One or more of the following.
In some embodiments, the molar concentration of the sodium salt in the electrolyte is 0.6-1.2mol/L.
In some embodiments, the sodium salt comprises NaPF 6 And sodium difluorooxalato borate (NaODFB).
NaPF is put into 6 In combination with NaODFB, can reduce NaPF 6 The hydrolysis resistance and stability of the electrolyte at high temperature are improved, so that the cycling stability of the sodium ion battery at high temperature can be improved.
In some embodiments, the NaPF 6 And NaODFB is (10-50): 1.
When NaPF is used 6 When the molar concentration of NaODFB is in the range, the sodium salt can obtain higher dissociation degree in the nonaqueous organic solvent, which is beneficial to dissociation of the sodium salt; the hydrolysis resistance and stability of the electrolyte at high temperature can be improved, so that the cycling stability of the sodium ion battery at high temperature can be improved.
In a second aspect, the application provides a sodium ion battery comprising the electrolyte according to the first aspect of the application.
By using a proper non-aqueous organic solvent and a first additive, the cycle performance of the sodium ion battery can be improved, and the gas yield of the sodium ion battery can be reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only drawings of some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a graph of the 55 ℃ cycle performance test of the batteries of example 1 and comparative example 1.
Detailed Description
Features and exemplary embodiments of various aspects of the present application will be described in detail below, and in order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described in further detail below with reference to the accompanying drawings and the detailed embodiments. It should be understood that the particular embodiments described herein are meant to be illustrative of the application only and not limiting. It will be apparent to one skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the application by showing examples of the application.
It should be noted that, in the present application, the terms "first," "second," and the like are used for distinguishing between similar objects and not for describing a particular sequential or chronological order. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises the element.
Unless otherwise indicated, the numerical values of the parameters set forth in the present application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of the present application). The test temperature for each of the parameters mentioned in the present application was 25℃and the test pressure was the standard atmospheric pressure, unless otherwise specified.
The term "one or more of" a list of connected items may mean any combination of the listed items. The term "plurality" means two or more.
The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value, and the range or value should be understood to include values close to the range or value. For numerical ranges, one or more new numerical ranges may be obtained in combination with each other between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point values, and are to be considered as specifically disclosed in the present application.
The embodiment of the application provides electrolyte for a sodium ion battery.
The electrolyte comprises a nonaqueous organic solvent, sodium salt and an additive. The nonaqueous organic solvent comprises a cyclic carbonate compound and a chain carbonate compound; the additive includes a first additive including sodium fluoride, sodium carbonate, and sodium oxide.
When the sodium ion battery is charged (i.e. formed) for the first time, a solid electrolyte interface film (SEI film for short) is formed on the surface of the negative electrode, and the SEI film is an excellent conductor of sodium ions and is a good electronic insulator. However, the SEI film consumes a part of sodium ions during formation, so that the first charge and discharge irreversible capacity of the sodium-ion battery increases. In the use process of the sodium ion battery, after the SEI film is damaged, electrolyte and sodium ions are consumed continuously, so that the capacity of the sodium ion battery is attenuated continuously, and the gas production rate of the sodium ion battery is increased.
The main components of the SEI film include organic sodium salt and inorganic sodium salt. Unlike lithium ion batteries, inorganic sodium salts have higher solubility in an electrolyte, and thus, breakage of an SEI film of a sodium ion battery at high temperature may be more remarkable.
The inventor researches and discovers that by adding sodium fluoride, sodium carbonate and sodium oxide into electrolyte at the same time, the compactness and uniformity of the SEI film can be improved, the dissolution degree of the SEI film is reduced, the consumption of the electrolyte and sodium ions can be reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature can be improved, and the gas production rate of the sodium ion battery can be reduced.
In some embodiments, the first additive may be present in an amount of 0.042 to 84ppm by mass based on the total mass of the electrolyte.
In the present application, ppm means mass concentration. For example, the mass content of the first additive in the electrolyte is 1ppm, which means that the ratio of the mass of the first additive in the electrolyte to the total mass of the electrolyte is 1:1000000.
Alternatively, the first additive may be present in an amount of 0.21 to 21ppm,0.50 to 15ppm,0.75 to 10ppm,1 to 6ppm by mass based on the total mass of the electrolyte.
Therefore, the compactness and uniformity of the SEI film can be further increased, the dissolution degree of the SEI film is reduced, the consumption of electrolyte and sodium ions can be further reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas yield of the sodium ion battery can be further reduced.
In some embodiments, the molar concentration of the first additive in the electrolyte may be 1-2000. Mu. Mol/L.
In some embodiments, the sodium fluoride may be present in an amount of 0.01 to 25ppm by mass based on the total mass of the electrolyte. Alternatively, the mass content of sodium fluoride may be 0.02-15ppm,0.03-10ppm,0.04-6ppm,0.1-6ppm,0.3-6ppm.
In some embodiments, the sodium carbonate may be present in an amount of 0.01 to 40ppm by mass based on the total mass of the electrolyte. Alternatively, the mass content of sodium carbonate may be 0.04-30ppm,0.07-20ppm,0.08-10ppm,0.2-10ppm,0.6-10ppm.
In some embodiments, the sodium oxide may be present in an amount of 0.01 to 25ppm by mass based on the total mass of the electrolyte. Alternatively, the mass content of sodium oxide may be 0.02-15ppm,0.03-10ppm,0.04-6ppm,0.1-6ppm,0.3-6ppm.
In some embodiments, the sodium fluoride may be present in an amount of 0.01 to 25ppm by mass, the sodium carbonate may be present in an amount of 0.01 to 40ppm by mass, and the sodium oxide may be present in an amount of 0.01 to 25ppm by mass, based on the total mass of the electrolyte.
Alternatively, the mass content of sodium fluoride may be 0.3 to 6ppm, the mass content of sodium carbonate may be 0.6 to 10ppm, and the mass content of sodium oxide may be 0.3 to 6ppm based on the total mass of the electrolyte.
By adjusting the mass content of sodium fluoride, sodium carbonate and sodium oxide within the above range, the compactness and uniformity of the SEI film can be further increased, and the dissolution degree of the SEI film can be reduced, so that the consumption of electrolyte and sodium ions can be further reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas yield of the sodium ion battery can be further reduced.
In some embodiments, the molar concentration of sodium fluoride in the electrolyte may be in the range of 0.3 to 933 μmol/L.
In some embodiments, the molar concentration of sodium carbonate in the electrolyte may be 0.2-592. Mu. Mol/L.
In some embodiments, the molar concentration of sodium oxide in the electrolyte may be in the range of 0.2 to 632. Mu. Mol/L.
In some embodiments, the mass ratio of sodium fluoride, sodium carbonate, and sodium oxide may be (0.6-7.1): 1-17.1): 1, based on the total mass of the electrolyte.
Alternatively, the mass ratio of sodium fluoride, sodium carbonate and sodium oxide may be (0.7-4): (1-7): 1, based on the total mass of the electrolyte.
By adjusting the mass ratio of sodium fluoride, sodium carbonate and sodium oxide in the above range, the compactness and uniformity of the SEI film can be further increased, and the dissolution degree of the SEI film can be reduced, so that the consumption of electrolyte and sodium ions can be further reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas yield of the sodium ion battery can be further reduced.
In some embodiments, the mass ratio of sodium fluoride to sodium carbonate may be (0.3-2.0): 1.
NaF is the main component of SEI film, has better electronic insulation and high mechanical strength, and can effectively reduce electrolyte decomposition and slow down the growth of sodium dendrite.
When the mass ratio of sodium fluoride to sodium carbonate in the electrolyte is within the above range, dissolution of NaF in the SEI film can be reduced, so that stability of the SEI film can be further improved, cycle performance of the sodium ion battery, particularly cycle performance at high temperature, can be further improved, and gas production amount of the sodium ion battery can be further reduced.
In some embodiments, the additive may further include a second additive, which may include one or more of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), 1, 3-propenesulfonic acid lactone (PST).
The second additive has film forming effect and can be used as film forming additive. The inventors have found that the addition of a film-forming additive only to an electrolyte contributes to formation of an SEI film of superior quality at the negative electrode, but it does not solve the problem of dissolution breakage of the SEI film well. The inventor further researches and discovers that by combining the first additive and the second additive, the compactness and uniformity of the SEI film can be further increased, the dissolution degree of the SEI film can be reduced, the consumption of electrolyte and sodium ions can be further reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas yield of the sodium ion battery can be further reduced.
VC is used as a film forming additive, has good high-temperature stability, and can improve the high-temperature stability of an SEI film, thereby improving the capacity and the cycle life of a sodium ion battery at high temperature.
The FEC can form a compact SEI film without increasing or obviously increasing the battery impedance, and in addition, the FEC can also derive fluorine-containing SEI films on the surfaces of the anode and the cathode, which is helpful for improving the deintercalation behavior of sodium ions at the interface of the electrodes and also is helpful for improving the cycle performance of the sodium ion battery at high temperature.
The DTD can increase the initial discharge capacity of the sodium ion battery, reduce the volume expansion rate of the sodium ion battery after being placed at high temperature, and improve the charge and discharge performance of the sodium ion battery. In the chemical process, the DTD can firstly generate reduction reaction on the surface of the negative electrode by a nonaqueous organic solvent, and sodium alkyl carbonate (ROCO) is formed on the surface of the negative electrode 2 Na) and sodium carbonate (Na 2 CO 3 ) Therefore, the co-intercalation of the subsequent nonaqueous organic solvent molecules can be reduced, and the loss of the first irreversible capacity of the sodium ion battery is reduced.
PST can form stable SEI film on the surface of the electrode of the sodium ion battery, reduce the reduction and decomposition of the nonaqueous organic solvent, reduce the gas production amount of the sodium ion battery at high temperature and improve the high-temperature performance of the sodium ion battery.
Thus, by combining one or more of the above compounds with the first additive, the cycle performance of the sodium ion battery, particularly at high temperatures, can be further improved, and the gas production of the sodium ion battery can be further reduced.
In some embodiments, the second additive may include both Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and 1, 3-propenesulfonic acid lactone (PST).
The VC and the FEC are matched to form a stable SEI film on the surface of the negative electrode, so that the decomposition of the electrolyte is reduced, and the normal-temperature circulation stability and the high-temperature circulation stability of the electrolyte are improved.
VC can improve the reversible capacity and high-temperature performance of the sodium ion battery, but can reduce the rate performance of the sodium ion battery; the FEC can improve the cycling stability and the multiplying power performance of the sodium ion battery; the PST can improve the high-temperature performance of the sodium ion battery and reduce the gas production rate of the sodium ion battery at high temperature; the DTD can improve the first coulombic efficiency and the cycle performance of the sodium ion battery.
When the second additive in the electrolyte simultaneously comprises the components, the stability of the sodium ion battery at high temperature can be further improved.
In some embodiments, the second additive may be present in the electrolyte in an amount of 0.5% -5% by mass, based on the total mass of the electrolyte, for example, may be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range of any two values recited above.
When the mass content of the second additive in the electrolyte is in the above range, the electrolyte can have better high-temperature stability, and a denser and uniform SEI film can be formed on the negative electrode, so that the high-temperature performance of the sodium ion battery can be better improved.
In some embodiments, the second additive may include both Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and 1, 3-propenesulfonic acid lactone (PST), and the mass ratio of vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, and 1, 3-propenesulfonic acid lactone may be (0.5-3): 0.2-1.
When the second additive is in the above range, VC may preferentially form NaF and Na on the surface of the anode 2 CO 3 Whereby it is possible to work synergistically with the first additive,and the film forming speed and uniformity of the SEI film are improved.
In some embodiments, the mass ratio of the first additive to the second additive may be (1.2X10 -6 - 1×10 -2 ):1. Alternatively, the mass ratio of the first additive to the second additive may be (5×10 -6 - 2.5×10 -3 ）:1，（6.2×10 -6 - 6.2×10 -4 ）:1，（2×10 -5 - 6.2×10 -4 ）:1。
In the formation process of the sodium ion battery, the second additive in the electrolyte can be decomposed on the surface of the negative electrode preferentially to form solid components which are deposited on the surface of the negative electrode active material, the just-generated solid components can play a role similar to crystal nucleus, and the first additive in the electrolyte can be rapidly separated out on the surface of the solid components, so that the generation speed of an SEI film and the uniformity and compactness of the SEI film can be improved.
When the mass ratio of the first additive to the second additive in the electrolyte is in the above range, a compact and uniform SEI film can be rapidly generated on the surface of the negative electrode through the synergistic combination of the first additive and the second additive, so that the dissolution and breakage of the SEI film in the use process of the sodium ion battery can be reduced, the cycle performance of the sodium ion battery, particularly the cycle performance at high temperature, can be further improved, and the gas yield of the sodium ion battery can be further reduced.
The inventor finds that when the mass ratio of the first additive to the second additive is larger, the second additive is unfavorable to play a role similar to a crystal nucleus, thereby affecting the rapid crystallization and precipitation of the first additive, reducing the generation speed of an SEI film, consuming more electrolyte to form the SEI film, and reducing the first coulomb efficiency reduction of the sodium ion battery; meanwhile, the uniformity of the formed SEI film is not improved, and the cycle performance of the sodium ion battery is further affected.
In some embodiments, the second additive may include both Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and 1, 3-propenesulfonic acid lactone (PST), and the mass ratio of the first additive to the second additive may be (1.2)×10 -6 - 1×10 -2 ):1. Alternatively, the mass ratio of the first additive to the second additive may be (5×10 -6 - 2.5×10 -3 ）:1，（6.2×10 -6 - 6.2×10 -4 ）:1，（2×10 -5 - 6.2×10 -4 ）:1。
In some embodiments, the mass ratio of cyclic carbonate compound to chain carbonate compound may be (0.2-0.7): 1.
The cyclic carbonate compound can raise the dielectric constant of electrolyte and is favorable to dissociation of sodium salt; the viscosity of the chain carbonate compound is lower. By adjusting the mass ratio of the cyclic carbonate compound to the chain carbonate compound within the above range, the electrolyte can have high ionic conductivity, thereby being beneficial to improving the cycle performance and/or the rate performance of the sodium ion battery.
In some embodiments, the cyclic carbonate compound may include one or more of Ethylene Carbonate (EC), propylene Carbonate (PC).
In some embodiments, the cyclic carbonate compound may include both Ethylene Carbonate (EC) and Propylene Carbonate (PC).
EC has a high dielectric constant, and can raise the dielectric constant of the electrolyte, thereby facilitating dissociation of sodium salt, and in addition, EC contributes to formation of stable SEI film. PC can enhance the conductivity of sodium ions, and in addition, PC can reduce the decomposition of the electrolyte.
Therefore, when the cyclic carbonate compound is in the above range, the electrolyte can be made to have higher ionic conductivity, thereby contributing to further improvement of the cycle performance and/or rate performance of the sodium ion battery.
In some embodiments, the chain carbonate compound may include one or more of diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), and methylpropyl carbonate (MPC).
In some embodiments, the chain carbonate compound may include one or both of diethyl carbonate (DEC) and ethylmethyl carbonate (EMC).
When the chain carbonate compound is in the above range, the viscosity of the electrolyte can be reduced, the ionic conductivity of the electrolyte can be improved, and the cycle performance of the sodium ion battery can be further improved.
In some embodiments, the nonaqueous organic solvent may include ethylene carbonate, propylene carbonate, and diethyl carbonate. Alternatively, the mass content of ethylene carbonate may be 5% to 30%, the mass content of propylene carbonate may be 15% to 40%, and the mass content of diethyl carbonate may be 30% to 80%, based on the total mass of the nonaqueous organic solvent.
In some embodiments, the nonaqueous organic solvent may include ethylene carbonate, propylene carbonate, and ethyl methyl carbonate. Alternatively, the mass content of ethylene carbonate may be 5% to 30%, the mass content of propylene carbonate may be 15% to 40%, and the mass content of methylethyl carbonate may be 30% to 80%, based on the total mass of the nonaqueous organic solvent.
In some embodiments, the nonaqueous organic solvent may include ethylene carbonate, propylene carbonate, diethyl carbonate, and ethylmethyl carbonate. Alternatively, the mass content of ethylene carbonate may be 5% to 30%, the mass content of propylene carbonate may be 15% to 40%, the mass content of diethyl carbonate may be 15% to 40%, and the mass content of ethylmethyl carbonate may be 15% to 40% based on the total mass of the nonaqueous organic solvent.
When the nonaqueous organic solvent is in the above range, the dielectric constant of the electrolyte can be increased, the viscosity of the electrolyte can be reduced, and the mobility of sodium ions can be increased, so that the cycle performance of the sodium ion battery can be improved.
In some embodiments, the sodium salt may comprise NaPF 6 Sodium difluorooxalato borate (NaODFB), naClO 4 、NaBF 4 、NaAsF 6 、NaSO 3 CF 3 、Na[(FSO 2 ) 2 N]、Na[(CF 3 SO 2 ) 2 N]One or more of the following.
In some embodiments, the molar concentration of sodium salt in the electrolyte may be 0.6-1.2mol/L, for example, may be 0.6mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1mol/L, 1.1mol/L, 1.2mol/L, or a range of any two of the foregoing values.
In some embodiments, the sodium salt may comprise NaPF 6 、NaODFB、Na[(FSO 2 ) 2 N]、Na[(CF 3 SO 2 ) 2 N]One or more of the following.
In some embodiments, the sodium salt may comprise NaPF 6 And NaODFB.
NaPF 6 The electrolyte can be easily dissociated in a nonaqueous organic solvent, and thus has good ionic conductivity. However, naPF 6 The high temperature stability of (c) is poor and easy to hydrolyze to generate HF, which can erode the electrode and SEI film. NaPF is put into 6 In combination with NaODFB, can reduce NaPF 6 The hydrolysis resistance and stability of the electrolyte at high temperature are improved, so that the cycling stability of the sodium ion battery at high temperature can be improved.
In some embodiments, the NaPF 6 The molar concentration in the electrolyte may be 0.55 to 1.1mol/L.
In some embodiments, the molar concentration of NaODFB in the electrolyte may be in the range of 0.01-0.1mol/L.
In some embodiments, the sodium salt may comprise NaPF 6 And NaODFB, naPF 6 The molar concentration of NaODFB in the electrolyte is 0.55-1.1mol/L, and the molar concentration of NaODFB in the electrolyte is 0.01-0.1mol/L.
When NaPF is used 6 When the molar concentration of NaODFB is in the range, the sodium salt can obtain higher dissociation degree in the nonaqueous organic solvent, which is beneficial to dissociation of the sodium salt; the hydrolysis resistance and stability of the electrolyte at high temperature can be improved, so that the cycling stability of the sodium ion battery at high temperature can be improved.
In some embodiments, the sodium salt may comprise NaPF 6 And NaODFB, naPF 6 And NaODFB may be present in a molar ratio of (10-50): 1.
When NaPF is used 6 When the molar ratio of NaODFB is in the range, the sodium salt can obtain higher dissociation degree in the nonaqueous organic solvent, which is beneficial to dissociation of the sodium salt; can also promote electricityHydrolysis resistance and stability of the electrolyte at high temperature, so that the cycling stability of the sodium ion battery at high temperature can be improved.
In some embodiments, the electrolyte may be prepared as follows.
Adding the non-aqueous organic solvent into a container, and stirring for 5-20min at 50-70deg.C and stirring speed of 250-350 r/min, wherein the non-aqueous organic solvent can be added into the container at one time or in batches; adjusting the temperature to 15-25 ℃, continuously stirring for 15-25min to stabilize the temperature of the non-aqueous organic solvent at 20+/-2 ℃, adding sodium salt, stirring for 25-35min to fully dissolve the sodium salt, and controlling the temperature at 20+/-2 ℃ in the whole stirring process; adding the additive into a container, and stirring at a stirring speed of 250-350 r/min for 25-35min to obtain electrolyte, wherein the additive can be added into the container at one time or in batches.
The embodiment of the application also provides a sodium ion battery, which comprises the electrolyte provided by the embodiment of the application.
The sodium ion battery also includes a positive electrode sheet.
The material, composition, and method of making the positive electrode sheet may include any technique known in the art.
In some embodiments, the positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.
The material of the positive electrode current collector is not particularly limited, and a material having electron conductivity may be selected. For example, aluminum foil, carbon coated aluminum foil may be used for the positive electrode current collector.
The positive electrode active material layer includes a positive electrode active material. The positive electrode active material may be selected from materials capable of absorbing and releasing sodium. The specific kind of the positive electrode active material is not particularly limited and may be selected according to the need. As an example, the positive electrode active material may include, but is not limited to, one or more of transition metal layered oxides, polyanion compounds, prussian blue analogues. These materials may be used singly or in combination of two or more.
The modifying compound for each positive electrode active material may be a doping modification, a surface coating modification, or a doping coating simultaneous modification for the positive electrode active material. In some embodiments, the positive electrode active material may include a composite material of sodium ferrous sulfate and carbon nanotubes, and the carbon nanotube content may be 5% or less.
When the composite material of the sodium ferrous sulfate and the carbon nano tube is adopted as the positive electrode active material, the positive electrode active material can be well matched with the electrolyte in the application, so that the high-temperature stability of the SEI film can be improved, the first coulombic efficiency and the capacity retention rate of the sodium ion battery can be improved, and the gas production of the sodium ion battery at high temperature can be reduced.
In some embodiments, the positive electrode active material layer may include a positive electrode conductive agent. The positive electrode conductive agent may include, but is not limited to, one or more of conductive carbon black, carbon nanotubes, acetylene black, and graphene.
In some embodiments, the positive electrode active material layer may include a positive electrode binder. The positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers.
In some embodiments, the areal density of the positive electrode active material layer on one side of the positive electrode current collector may be 9.5-17.5mg/cm 2 。
In some embodiments, the positive electrode sheet may be prepared, for example, by a coating method, that is, dispersing materials such as a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, etc., in a solvent, for example, N-methylpyrrolidone (NMP), to prepare a slurry; and then coating the slurry on the surface of one side or two sides of the positive electrode current collector, and drying, rolling and the like to obtain the positive electrode plate.
The sodium ion battery may further include a negative electrode sheet.
The material, composition, and method of making the negative electrode sheet may include any technique known in the art.
In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
The material of the negative electrode current collector is not particularly limited, and a material having electron conductivity may be selected. For example, the negative electrode current collector may employ aluminum foil.
The anode active material layer includes an anode active material. The specific kind of the anode active material is not particularly limited, and may be selected according to the need. As an example, the anode active material may include hard carbon.
In some embodiments, the anode active material layer may include an anode conductive agent. The negative electrode conductive agent may include, but is not limited to, one or more of conductive carbon black, carbon nanotubes, acetylene black, and graphene.
In some embodiments, the anode active material layer may include an anode binder. The negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber, carboxymethyl cellulose.
In some embodiments, the areal density of the anode active material layer on one side of the anode current collector may be 2.5-6.5mg/cm 2 。
In some embodiments, the negative electrode sheet may be prepared, for example, by a coating method, that is, dispersing materials such as a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, etc. in a solvent (e.g., deionized water) to prepare a slurry; and then coating the slurry on the surface of one side or two sides of the negative electrode current collector, and drying, rolling and the like to obtain the negative electrode plate.
The sodium ion battery may also include a separator. The diaphragm can be arranged between the positive plate and the negative plate and mainly plays a role in preventing the positive electrode and the negative electrode from being short-circuited.
In some embodiments, the separator may include a polyethylene film, a polypropylene film, or a fiberglass film.
Sodium ion batteries can be prepared by the steps of: sequentially stacking and fixing the positive plate, the diaphragm and the negative plate, putting the positive plate, the diaphragm and the negative plate into an outer package (for example, a semi-sealed aluminum plastic film) together, sealing, drying (for example, drying under the vacuum condition of 80-90 ℃ for 40-60 h), injecting electrolyte after the drying is finished, and carrying out the procedures of vacuum packaging, formation and the like to obtain the sodium ion battery.
Examples
The present disclosure is more particularly described in the following examples that are intended as illustrations only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages and ratios reported in the examples below are on a mass basis, and all reagents used in the examples are commercially available or were obtained synthetically according to conventional methods and can be used directly without further treatment, as well as the instruments used in the examples.
Test part
(1) First coulombic efficiency test of sodium ion battery
Standing the sodium ion battery for 24 hours at 25 ℃ to enable the electrolyte to fully infiltrate the anode and the cathode and the diaphragm; charging the sodium ion battery after standing for 120min at a constant current of 0.05C (1 C=120 mA/g current density), and recording the charging capacity as C1; charging the sodium ion battery for 180min at a constant current of 0.1C, and recording the charging capacity as C2; standing for 2h, and then charging the sodium ion battery to 4.5V at a constant current of 0.1C, wherein the charging capacity is recorded as C3, and the total charging capacity is C1+C2+C3; and finally, discharging the sodium ion battery to 2.0V at a constant current of 0.1C to obtain the discharge capacity, and completing the formation of the first circle. The ratio of the first discharge capacity to the first charge capacity of the sodium ion battery is the first coulombic efficiency of the sodium ion battery, i.e. the first coulombic efficiency=discharge capacity/total charge capacity×100% of the sodium ion battery.
(2) Cycling capacity retention test for sodium ion batteries
Charging the sodium ion battery to a voltage of 4.5V at a constant current of 0.2C at 25 ℃, discharging to a voltage of 2V at a constant current of 0.2C, and testing the discharge capacity of the sodium ion battery and marking as C0; the cycle charge and discharge were repeated under the same conditions as described above, and the discharge capacity of the sodium ion battery after the 200 th cycle was measured and recorded as C1. Capacity retention after 200 cycles of sodium ion battery at 25 ℃ = C1/c0×100%.
Charging the sodium ion battery to a voltage of 4.5V at a constant current of 0.2C at 55 ℃, discharging to a voltage of 2V at a constant current of 0.2C, and testing the discharge capacity of the sodium ion battery and marking as C2; the cycle charge and discharge were repeated under the same conditions as described above, and the discharge capacity of the sodium ion battery after the 200 th cycle was measured and recorded as C3. Capacity retention after 200 cycles of sodium ion battery at 55 ℃ = C3/C2 x 100%.
(3) Volume expansion rate test of sodium ion battery
The volume of the sodium ion battery was measured by a drainage method at 25℃and denoted as V1, and the sodium ion battery was again measured by a drainage method and denoted as V2 after 200 cycles according to the measurement method of the retention rate of the circulating capacity at 25℃in the above test (2). The volume expansion ratio of the sodium ion battery is (V2-V1)/V1 multiplied by 100 percent.
Example 1
(1) Preparation of electrolyte
In an argon atmosphere glove box, 10g of ethylene carbonate was charged into a three-necked flask equipped with a stirrer and a thermometer, and stirred at a temperature of 60℃and a stirring speed of 300 rpm for 10 minutes. After the ethylene carbonate was completely melted, 30g of propylene carbonate and 60g of diethyl carbonate were added, and stirring was continued for 25 minutes to obtain a mixed solution A.
The temperature was adjusted to 20℃and stirring was continued for 20 minutes to stabilize the temperature of the mixed solution A at 20℃and then 12.92g of NaPF was added to a three-necked flask 6 And 0.68g NaODFB, and stirring for 30min to dissolve thoroughly, to obtain a mixed solution B. The temperature during stirring was stabilized at 20 ℃.
The second additives of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD) and 1, 3-propenesulfonic acid lactone (PST) were added to the mixed solution B in amounts of 1.13g, 0.568g and 1.7g, respectively, and then stirred at a rotation speed of 300 rpm for 30 minutes to obtain a mixed solution C.
Weigh 4.725×10 separately -5 g NaF、7.95×10 -5 g Na 2 CO 3 、4.65×10 -5 g Na 2 O is used as a first additive and added into the mixed solution C, and the mixed solution C is stirred for 30min at the rotating speed of 300 rpm to obtainTo the electrolyte. The total mass content of the first additive in the electrolyte was 1.47ppm, and the mass ratio of the first additive to the second additive (i.e., the ratio of the total mass of the first additive to the total mass of the second additive) was 4.3X10 -5 :1。
(2) Preparation of positive plate
Na is mixed with 1.2 Fe(SO 4 ) 1.6 CNT-5%, super-p and polyvinylidene fluoride are dispersed in N-methyl pyrrolidone according to the mass ratio of 92:2:6, and the slurry with the solid content of 50% is obtained after uniform mixing. Coating the slurry on two surfaces of carbon-coated aluminum foil, drying at 120deg.C under vacuum for 12 hr, and rolling to a compaction density of 2g/cm 3 The thickness of the positive electrode active material layer was 82.5 μm, and then a tab was welded to obtain a positive electrode sheet. The positive plate is die-cut into square positive plates with the width of 43mm and the length of 56mm, and the length of the tab is 8mm and the width is 6mm. The thickness of the carbon layer on the surface of the carbon-coated aluminum foil is 1 mu m.
(3) Preparation of negative electrode sheet
Hard carbon, super-p, styrene-butadiene rubber and carboxymethyl cellulose are dispersed in deionized water according to the mass ratio of 95:1.5:2:1.5, and the slurry with the solid content of 54% is obtained after uniform mixing. The slurry was coated on both surfaces of an aluminum foil, dried under vacuum at 120℃for 12 hours, and then rolled to a compacted density of 1.0g/cm 3 The thickness of the negative electrode active material layer was 50 μm, and then a tab was welded to obtain a negative electrode sheet. The negative electrode sheet was die-cut into square negative electrode sheets 45mm in width and 58mm in length, and tabs 7mm in length and 6mm in width.
(4) Sodium ion battery preparation
And stacking the positive plate, the diaphragm and the negative plate according to the sequence of the positive plate, the diaphragm and the negative plate, winding and fixing, then placing into a semi-sealed aluminum-plastic film, performing top sealing and side sealing, transferring to a vacuum condition at 85 ℃ for drying for 48 hours, injecting electrolyte, and performing vacuum packaging to obtain the sodium ion battery.
Example 2
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the mass content of the first additive, the mass ratio of the first additive to the second additive were different.
According to NaF, na 2 CO 3 、Na 2 The mass ratio of O is 4.725:7.95:4.65, and NaF and Na are respectively weighed 2 CO 3 And Na (Na) 2 O, and the total mass content of the first additive was 0.042ppm.
The mass ratio of the first additive to the second additive is 1.2X10 -6 :1。
Example 3
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the mass content of the first additive, the mass ratio of the first additive to the second additive were different.
According to NaF, na 2 CO 3 、Na 2 The mass ratio of O is 4.725:7.95:4.65, and NaF and Na are respectively weighed 2 CO 3 And Na (Na) 2 O, and the total mass content of the first additive was 84ppm.
The mass ratio of the first additive to the second additive is 2.5X10 -3 :1。
Example 4
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the mass content of the first additive, the mass ratio of the first additive to the second additive were different.
According to NaF, na 2 CO 3 、Na 2 The mass ratio of O is 4.725:7.95:4.65, and NaF and Na are respectively weighed 2 CO 3 And Na (Na) 2 O, and the total mass content of the first additive was 0.21ppm.
The mass ratio of the first additive to the second additive is 6.2X10 -6 :1。
Example 5
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the mass content of the first additive, the mass ratio of the first additive to the second additive were different.
According to NaF, na 2 CO 3 、Na 2 The mass ratio of O is 4.725:7.95:4.65, and NaF and Na are respectively weighed 2 CO 3 And Na (Na) 2 O, and the total mass content of the first additive was 21ppm.
The mass ratio of the first additive to the second additive is 6.2X10 -4 :1。
The composition of the additives for the electrolytes of examples 1-5 is shown in Table 1.
The test results of the batteries of examples 1 to 5 are shown in table 2, and the cycle performance test chart at 55 c of the battery of example 1 is shown in fig. 1.
TABLE 1
TABLE 2
As can be seen from tables 1 and 2, when the first additive is included in the electrolyte, the first coulombic efficiency, the retention of the circulating capacity at 25 ℃, the retention of the circulating capacity at 55 ℃ of the battery can be improved, and the volume expansion rate of the battery can be reduced.
As is clear from tables 1 and 2, the mass content of the first additive and the mass ratio of the first additive to the second additive were slightly different, and the test results were slightly different when the mass content of the first additive was between 0.21 and 21ppm, the mass ratio of the first additive to the second additive was between (6.2X10 -6 :1）-（6.2×10 -4 1), the first coulomb efficiency, the circulation capacity retention rate at 25 ℃ and the circulation capacity retention rate at 55 ℃ of the battery can be further improved, and the volume expansion rate of the battery can be further reduced.
Example 6
In addition to the preparation of the electrolyte, naF and Na in the electrolyte 2 CO 3 、Na 2 The preparation process was the same as in example 1 except that the O mass ratio was 2.94:7.42:4.34. And the total mass content of the first additive in the electrolyte was 1.47ppm.
Example 7
In addition to the preparation of the electrolyte, naF and Na in the electrolyte 2 CO 3 、Na 2 The preparation process was the same as in example 1 except that the O mass ratio was 8.17:4.12:2.41. And the total mass content of the first additive in the electrolyte was 1.47ppm.
Example 8
In addition to the preparation of the electrolyte, naF and Na in the electrolyte 2 CO 3 、Na 2 The preparation process was the same as in example 1 except that the O mass ratio was 1.63:8.24:4.82. And the total mass content of the first additive in the electrolyte was 1.47ppm.
The test results for the cells of examples 6-8 are shown in table 3.
TABLE 3 Table 3
As can be seen from Table 3, when the mass content of the first additive is the same, but NaF and Na 2 CO 3 And Na (Na) 2 When the mass ratio of O is changed, the initial coulombic efficiency of the battery, the cyclic capacity retention at 25 ℃, the cyclic capacity retention at 55 ℃ and the volume expansion rate of the battery are slightly different.
It can also be seen from Table 3 that when NaF and Na 2 CO 3 When the mass ratio of (2) is between 0.3:1 and 2:1, the first coulombic efficiency, the cyclic capacity retention rate at 25 ℃ and the cyclic capacity retention rate at 55 ℃ of the battery can be further improved, and the volume expansion rate of the battery can be reduced.
Example 9
The preparation process was the same as in example 1 except that the second additive composition was different in the preparation of the electrolyte.
The second additive included only VC and was added in a mass of 4g.
Example 10
The preparation process was the same as in example 1 except that the second additive composition was different in the preparation of the electrolyte.
The second additive included only FEC and was added in a mass of 4g.
Example 11
The preparation process was the same as in example 1 except that the second additive composition was different in the preparation of the electrolyte.
The second additive included only DTD and was added in a mass of 4g.
Example 12
The preparation process was the same as in example 1 except that the second additive composition was different in the preparation of the electrolyte.
The second additive included only PST and was added at a mass of 4g.
Example 13
The preparation process was the same as in example 1 except that no second additive was added in the preparation of the electrolyte.
Example 14
Except for the preparation of the electrolyte, naODFB and NaPF were not added 6 Except that the mass of (C) was 13.6g, the preparation process was the same as in example 1.
The test results for the batteries of examples 9-14 are shown in table 4.
TABLE 4 Table 4
As is also apparent from table 4, when the second additive was further added to the electrolyte, the first coulombic efficiency, the cycle capacity retention at 25 ℃ and the cycle capacity retention at 55 ℃ of the battery were further improved, and the volume expansion rate of the battery was further reduced.
It is also apparent from table 4 that when the second additive includes the above four components (i.e., VC, FEC, DTD and PST) at the same time, the initial coulombic efficiency, the cyclic capacity retention at 25 ℃ and the cyclic capacity retention at 55 ℃ of the battery are further improved, while the volumetric expansion rate of the battery is further reduced.
It can also be seen from Table 4 that when the sodium salt includes NaPF at the same time 6 And NaODFB capable of reacting with NaPF 6 By matching, the first coulomb efficiency, the cycle capacity retention rate at 25 ℃ and the cycle capacity retention rate at 55 ℃ of the battery can be further improved, and the volume expansion rate of the battery can be further reduced.
Comparative example 1
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the first additive composition was different and the second additive was not added.
The first additive included only NaF and its mass content in the electrolyte was 1.47ppm.
Comparative example 2
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the first additive composition was different and the second additive was not added.
The first additive comprises Na only 2 CO 3 And its mass content in the electrolyte was 1.47ppm.
Comparative example 3
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the first additive composition was different and the second additive was not added.
The first additive comprises Na only 2 O and its mass content in the electrolyte was 1.47ppm.
Comparative example 4
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the first additive composition was different and the second additive was not added.
The first additive comprises NaF and Na 2 CO 3 NaF and Na 2 CO 3 The mass ratio of the first additive was 4.725:7.95, and the total mass content of the first additive in the electrolyte was 1.47ppm.
Comparative example 5
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the first additive composition was different and the second additive was not added.
The first additive comprises Na 2 CO 3 And Na (Na) 2 O，Na 2 CO 3 And Na (Na) 2 The mass ratio of O was 7.95:4.65, and the total mass content of the first additive in the electrolyte was 1.47ppm.
Comparative example 6
The preparation process was the same as in example 1 except that in the preparation of the electrolyte, the first additive composition was different and the second additive was not added.
The first additive comprises NaF and Na 2 O, naF and Na 2 The mass ratio of O was 4.725:4.65, and the total mass content of the first additive in the electrolyte was 1.47ppm.
Comparative example 7
The preparation process was the same as in example 1 except that the first additive and the second additive were not added in the preparation of the electrolyte.
The test results of the batteries of comparative examples 1 to 7 are shown in table 5, and the cycle performance test chart at 55 c of the battery of comparative example 1 is shown in fig. 1.
TABLE 5
As is clear from table 5, when only any one component or any two components of the first additive are contained in the electrolyte, the effect of improving the initial coulombic efficiency, the cyclic capacity retention at 25 ℃, the cyclic capacity retention at 55 ℃ and the effect of reducing the volume expansion rate of the battery are not good even if the content and the ratio thereof are within the scope of the present application.
From examples 1 to 14 and comparative examples 1 to 7, it is understood that the battery of the present application has a first coulombic efficiency of 78.9% or more, a cycle capacity retention of 91.2% or more at 25 ℃ and a cycle capacity retention of 81.0% or more at 55 ℃ and can have a volume expansion rate of less than 13.3%.
While the application has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes and substitutions of equivalents may be made and equivalents will be apparent to those skilled in the art without departing from the scope of the application. Therefore, the protection scope of the application is subject to the protection scope of the claims.

Claims (11)

1. An electrolyte for sodium ion battery comprises nonaqueous organic solvent, sodium salt and additive, and is characterized in that,
the nonaqueous organic solvent comprises a cyclic carbonate compound and a chain carbonate compound;
the additive comprises a first additive comprising sodium fluoride, sodium carbonate and sodium oxide;
the mass content of the first additive is 0.042-84ppm based on the total mass of the electrolyte;
the additive further comprises a second additive comprising one or more of vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, 1, 3-propenesulfonic acid lactone.
2. The electrolyte according to claim 1, wherein the electrolyte is a liquid containing, based on the total mass of the electrolyte,
The mass content of the sodium fluoride is 0.01-25ppm; and/or the number of the groups of groups,
the mass content of the sodium carbonate is 0.01-40ppm; and/or the number of the groups of groups,
the mass content of the sodium oxide is 0.01-25ppm.
3. The electrolyte according to claim 2, wherein the first additive satisfies at least one of the following conditions (1) to (2):
(1) The mass ratio of the sodium fluoride to the sodium carbonate to the sodium oxide is (0.6-7.1): 1-17.1): 1;
(2) The mass ratio of the sodium fluoride to the sodium carbonate is (0.3-2.0): 1.
4. The electrolyte according to claim 1, wherein the mass content of the second additive in the electrolyte is 0.5% to 5% based on the total mass of the electrolyte.
5. The electrolyte of claim 1 wherein the second additive comprises vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, and 1, 3-propenolactone, and the mass ratio of the vinylene carbonate, the fluoroethylene carbonate, the ethylene sulfate, and the 1, 3-propenolactone is (0.5-3): 0.2-1.
6. The electrolyte of claim 1, wherein the mass ratio of the first additive to the second additive is (1.2 x 10 -6 - 1×10 -2 ）:1。
7. The electrolyte of claim 6, wherein the mass ratio of the first additive to the second additive is (6.2 x 10 -6 - 6.2×10 -4 ）:1。
8. The electrolyte according to claim 1, wherein the mass ratio of the cyclic carbonate compound to the chain carbonate compound is (0.2-0.7): 1.
9. The electrolyte according to claim 1, wherein the sodium salt further satisfies at least one of the following conditions (1) to (2):
(1) The sodium salt comprises NaPF 6 Sodium difluorooxalato borate, naClO 4 、NaBF 4 、NaAsF 6 、NaSO 3 CF 3 、Na[(FSO 2 ) 2 N]、Na[(CF 3 SO 2 ) 2 N]One or more of the following;
(2) The molar concentration of the sodium salt in the electrolyte is 0.6-1.2mol/L.
10. The electrolyte of claim 9 wherein the sodium salt comprises NaPF 6 And sodium difluorooxalato borate, and NaPF 6 And sodium difluorooxalato borate in a molar ratio of (10-50): 1.
11. A sodium ion battery comprising the electrolyte of any one of claims 1-10.
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CN116454389A (en) * 2023-05-29 2023-07-18 远景动力技术(江苏)有限公司 Secondary battery electrolyte and application thereof

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CN115088112A (en) * 2020-02-27 2022-09-20 株式会社日本触媒 Composition, electrolyte material, and electrolyte
CN113991177A (en) * 2021-10-25 2022-01-28 天津市捷威动力工业有限公司 Non-aqueous electrolyte of sodium-ion battery and application thereof
CN116454389A (en) * 2023-05-29 2023-07-18 远景动力技术(江苏)有限公司 Secondary battery electrolyte and application thereof

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